Talk:Pressurized water reactor
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[edit] Cleanup / Rewrite
I'm planing to do some cleanup and/or rewriting of this article over the next few days. In particular I'm planing to remove a lot of the stuff that is already covered in nuclear reactor leaving the bits that distinguish a PWR from other reactor types ( this appears to be the trend in other articles on special reactor types ). Please feel free to replace any material I remove if you feel it should remain. J.Ring 17:55, 10 September 2006 (UTC)
- I'm going to remove the context tag as I think the introduction and general article is now a lot softer and more in line with other articles on various reactor types. J.Ring 20:19, 10 September 2006 (UTC)
I copied the Overview section's first sentence in again since it got lost in the Sep 10 edit. Was there a specific reason for that deletion? (Other than removing things covered elsewhere.) Mentioning the goal first makes the following details comprehensible, especially for non-technical readers. I think in a section called "Overview" it's justified to feature that information, especially if it's only one sentence. Removing redundance is good, but don't overdo it, we shouldn't drive people away by requiring them to read 4000 other articles first ;-) -- 193.99.145.162 19:06, 21 November 2006 (UTC)
[edit] A lot to do
Quite a lot still to do on this page. For example, a PWR is *not* fully thermalised as this page currently claims. A CANDU is, and a graphite-moderated reactor is, but in a PWR or BWR the neutron loss from capture in the light water means that the core must be as compact as possible, so it's a compromise. Not quite sure how to put this simply.
Quite a lot of the information really belongs in the nuclear fission or nuclear reactor pages, as it applies to any reactor, not just to a PWR. Andrewa 06:19, 21 Aug 2003 (UTC)
- That's possibly true, but what strikes me the most is the paragraph about reaction control through delayed neutrons...that's something I didn't read anywhere else but is very pertinent.--Chealer 02:06, 2004 Nov 10 (UTC)
What's the difference between a VVER and a PWR? I've heard that VVER is the soviet design for PWR plants.
The Enrico Fermi 2 station is a BWR. I'm going to remove it from the list of PWR reactors. I suggest that someone check the other stations listed for similar problems.Sohlemac 18:30, 3 January 2006 (UTC)
- The VVER is basically just the soviet disign for a PWR like you said. There may be small differences, but I am not sure what they are. Lcolson 19:25, 3 January 2006 (UTC)
I Have a question about reactors in general. I dont understand why the steam needs to be condensed/cooled before going through the cycle again. Really simple version of the entire thing, reaction heats water, water heats other water, steam goes to turbine, then gets cooled, that is the step I dont understand because if the water/steam is cooled there doesn't it just need to be heated again to go back through the turbine? I know going through the turbine it will cool down but why cool it more than it needs to be? doesnt this lower efficency of the reactor? sorry if this is a simple question just dont know much about it. Caleb rosenberg 05:12, 20 February 2006 (UTC)
- The most ideal cycle possible is the carnot cycle, which when plotted on a T-s diagram is a box. In order for the greatest second-law efficiency to be obtained we want a real cycle to be as close to this "carnot box" as possible. In a real rankine cycle the condenser forms the "bottom leg" of the box (which is essential what a PWR cycle is). More to the point, by definition a rankine cycle is a heat engine, which must have a hot and cold side. In the rankine cycle the condenser facilitates the heat transfer for the cold side. In laymens terms, if you don't have a condenser the cycle will continue to heat up until something breaks. Not only that, but very little energy would be created from a process like this, because the water would have to remain superheated vapor for the whole cycle, which completely defeats the purpose of a rankine cycle. HTH! Wizard191 01:28, 23 February 2006 (UTC)
- Turbines operate most efficiently when the pressure at the inlet is much higher than the pressure at the outlet. When the steam is cooled it condenses to a liquid which lowers the pressure significantly. Thus by lowering the temperature of the water at the outlet, you can dramatically increase the efficiency of the turbine. Also, no turbine can convert 100% of the heat produced into electricity, thus if the reactor is not cooled it would eventually melt. This is called a loss of coolant accident, or LOCA. Btw Wizard, supercritical water is actually a very good working fluid precisely because it doesn't undergo phase changes. For this reason there is much work on Generation IV reactors cooled by supercritical water. 137.205.192.27 21:58, 3 September 2006 (UTC)
As a note it is easer to pump water than to pump steam when you are designing a reactor. This makes components significantly cheaper to build. Greenwjam 7:35 29 October 2006
[edit] Boric acid
"This is an advantage for the BWR design because boric acid is very corrosive and the complex charging and letdown system is not required."
It is my understanding that boric acid is not all that corrosive (Boric acid calls it a mild acid), but that, over a long time, (very) tiny leaks in the CRDM nozzles (the Alloy 600 sleeves that the control rod drive mecahnisms move in) to the head drip enough boric acid to make a problem. Comments? --nbach 04:17, 5 April 2006 (UTC)
Boric acid is not too corrosive at standard temperature and pressure but at reactor operating temperatures it is. I guess the word "very" is not a very technical term ;-) Perhaps it would be better to state that when boric acid solutions leak onto reactor system components at operating temperatures, corrosion can be a problem. 205.188.117.70 16:12, 5 July 2006 (UTC)
[edit] I belive this should be included in how pressureized water reactors work...
Inside a Nuclear Power Plant To build a nuclear reactor, what you need is some mildly enriched uranium. Typically, the uranium is formed into pellets with approximately the same diameter as a dime and a length of an inch or so. The pellets are arranged into long rods, and the rods are collected together into bundles. The bundles are then typically submerged in water inside a pressure vessel. The water acts as a coolant. In order for the reactor to work, the bundle, submerged in water, must be slightly supercritical. That means that, left to its own devices, the uranium would eventually overheat and melt.
To prevent this, control rods made of a material that absorbs neutrons are inserted into the bundle using a mechanism that can raise or lower the control rods. Raising and lowering the control rods allow operators to control the rate of the nuclear reaction. When an operator wants the uranium core to produce more heat, the rods are raised out of the uranium bundle. To create less heat, the rods are lowered into the uranium bundle. The rods can also be lowered completely into the uranium bundle to shut the reactor down in the case of an accident or to change the fuel.
Pulled From http://www.howstuffworks.com/nuclear-power.htm its quite accurate for some apps.
[edit] Huh?
"Since the mass of a water molecule is very similar to the size of a neutron..." What on earth does this mean? First, I don't see how "mass" and "size" can be considered meaningfully similar in the first place. Second, a typical water molecule will contain eight neutrons and ten protons, which is obviously far heavier than a single neutron. I don't know what the article is trying to say here, but unfortunately do not have the background knowledge to correct or clarify it. Egomaniac 19:22, 11 December 2006 (UTC)
Ahh thats easy. Its atomic mass. Its like your takeing two bowling balls and smaking them together if they are both the same mass you dissapate the most energy. However if one is significantly larger than the other than the smaller of the two will simply bounce off. The modarator is the H2 in the water molocuele. Hydrogen atoms have close to 1 mass unit as do neutrons => when a neutron strkies a water molocuel and interacts with the hydrogen it sheds energy. => energy released in the form of heat => also slows the neutron => due to a slower moveing partical is more likely to interact with matter than a fast moveing partical you get more interactions => slows the neutron further and genarates more heat => assuming your not useing a fast fission reactor you'll get a slow moveing netron (thermalised) headed back into the core => more likely to interact with fuel in the core => probability states that when it interacts it will release more neutrons and continues the cycle.
This is a VERRY rudamentry decription but it works for the purpous of explanation. greenwjam 31 DEC 2006
